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ATC (Animated Texture Collections) files are used to create small animated props. They are referenced by prop exemplars via RKT0 properties, but the animations share more in common with isometric models referenced by RKT1 properties.

Important Points

ATC files and their companion AVP files have some specific requirements and caveats:

  • Each ATC file must have a unique set of AVP files or the prop will appear in game as a brown box.
  • Multiple ATC files can reference the same source FSH. (Although this will cause incorrect animations in the Reader, they will appear correctly in game.)
  • ATC prop rotations are specified in a different order than S3D prop rotations. (This is not a problem for most standalone props, but traffic lights and RR crossings interact with stop points and static props and must be created correctly.)

Image:S3d vs atc rotations.png


ATC files are small files, always 48 bytes, that group together AVP files, a FSH image used as a frame source, and specify a number of frames. They also serve as the model reference for props, referenced using a RKT0 property or one state of a RKT4 property.

File Structure:

ATC files have the following file structure:

All WORDs and DWORDs are stored in little endian notation.

00: DWORD - ATC Type Value (always 29A5D1EC)
04: DWORD - Source FSH Type Value (always 7AB50E44)
08: DWORD - Source FSH Group Value (usually 2A2458F9, others may be valid but not tested)
0C: DWORD - Source FSH Instance Value
10: DWORD - AVP Type Value (always 09ADCD75)
14: DWORD - AVP Group Value (always 2A2458F9)
18: DWORD - Zoom 1 AVP Instance Value (usually 00000000 Animations are generally not visible at zooms 1 and 2)
1C: DWORD - Zoom 2 AVP Instance Value (usually 00000000 Animations are generally not visible at zooms 1 and 2)
20: DWORD - Zoom 3 AVP Instance Value
24: DWORD - Zoom 4 AVP Instance Value
28: DWORD - Zoom 5 AVP Instance Value
2C: DWORD - Number Of Frames

Visual Reference:

(Please note the little endian storage of the constants above.)

Image:ATC format.png

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